SPARTA, Inc. H Harney (SPARTA) INTERNET-DRAFT A Schuett (NSA) A Colegrove (SPARTA) SPARTA, Inc., National Security Agency draft-ietf-msec-gsakmp-light-sec-01.txt July 2002 GSAKMP Light Status of this memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress''. The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Document expiration: December 31, 2002 Abstract A protocol specification must balance two often conflicting goals: to produce as general a protocol as possible, and to produce a simple protocol. The Group Secure Association Key Management Protocol (GSAKMP) is a general protocol for creating and managing cryptographic groups on a network. This document describes the GSAKMP-Light (GL) profile, a way to shorten the number of messages exchanged during secure group establishment. The GSAKMP protocol assumed that group members joining a secure group had no information about the specific security mechanisms used by the group (for example, the key length, encryption protocol, etc). GSAKMP-Light provides a profile for the case where group members INTERNET-DRAFT GSAKMP Light July 2002 have been previously notified of these security mechanisms, used for joining a group, during the group announcement or invitation. This simplification removes 2 messages from the group establishment portion of the GSAKMP protocol, eliminates the need for initiating a unicast security association, and removes the need for many of the optional fields of individual messages. The profile does not sacrifice any of the security properties of the full protocol. To facilitate the transmission of security mechanism settings during session invitation or announcement, this document also describes a useful default set of security algorithms and configurations, Security Suite 1. Full specification of this suite allows an entire set of algorithms and settings to be described to prospective group members in a concise manner. Future security suites can be defined as needed. Copyright Notice Copyright (c) The Internet Society (2002). All Rights Reserved. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 2] INTERNET-DRAFT GSAKMP Light July 2002 Contents 1 Introduction 6 2 GSAKMP Light (GL) 7 2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 Basis of security 9 4 Sequence of events 10 5 Security Policy 11 6 Security Suite 1 (SS1) 11 6.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.2 Definition Suite 1 . . . . . . . . . . . . . . . . . . . . . . . . 11 7 Message Structure 12 7.1 Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.2 Light Request to Join . . . . . . . . . . . . . . . . . . . . . . . 13 7.3 Light Key Download . . . . . . . . . . . . . . . . . . . . . . . . 13 7.4 Light Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 13 7.5 Group Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.5.1Member Joins/Leaves . . . . . . . . . . . . . . . . . . . . . . 14 7.5.2Rekey Events . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.5.3Group Removal/Destruction . . . . . . . . . . . . . . . . . . . 15 8 GSAKMP Payload Structure 15 8.1 GSAKMP Header . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.2 Generic Payload Header . . . . . . . . . . . . . . . . . . . . . . 18 8.3 Data Attributes Payload . . . . . . . . . . . . . . . . . . . . . . 18 8.4 Policy Token Payload . . . . . . . . . . . . . . . . . . . . . . . 19 8.5 Key Download Payload . . . . . . . . . . . . . . . . . . . . . . . 20 8.5.1GTEK Key Packet . . . . . . . . . . . . . . . . . . . . . . . . 21 8.5.2Rekey Key Packet . . . . . . . . . . . . . . . . . . . . . . . . 22 8.6 Rekey Event Payload . . . . . . . . . . . . . . . . . . . . . . . . 23 8.7 Identification Payload . . . . . . . . . . . . . . . . . . . . . . 24 8.8 Authorization Payload . . . . . . . . . . . . . . . . . . . . . . . 25 8.9 Certificate Payload . . . . . . . . . . . . . . . . . . . . . . . . 26 8.10Certificate Request Payload . . . . . . . . . . . . . . . . . . . . 27 8.11Signature Payload . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.12Notification Payload . . . . . . . . . . . . . . . . . . . . . . . 30 8.12.1Notification Data - Acknowledgement (ACK) Message Type . . . . . 32 8.13Vendor ID Payload . . . . . . . . . . . . . . . . . . . . . . . . . 33 8.14Key Creation Payload . . . . . . . . . . . . . . . . . . . . . . . 34 8.15Nonce Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 9 References and authors addesses 36 9.1 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 9.2 Authors Addresses . . . . . . . . . . . . . . . . . . . . . . . . . 38 Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 3] INTERNET-DRAFT GSAKMP Light July 2002 List of Figures 1 GSAKMP Light Ladder Diagram . . . . . . . . . . . . . . . . . . . . 12 2 GSAKMP Header Format . . . . . . . . . . . . . . . . . . . . . . . 16 3 Generic Payload Header . . . . . . . . . . . . . . . . . . . . . . 18 4 Data Attributes Payload . . . . . . . . . . . . . . . . . . . . . . 19 5 Policy Token Payload Format . . . . . . . . . . . . . . . . . . . . 19 6 Key Download Payload Format . . . . . . . . . . . . . . . . . . . . 20 7 Rekey Event Payload Format . . . . . . . . . . . . . . . . . . . . 23 8 Identification Payload Format . . . . . . . . . . . . . . . . . . . 24 9 Authorization Payload Format . . . . . . . . . . . . . . . . . . . 25 10 Certificate Payload Format . . . . . . . . . . . . . . . . . . . . 26 11 Certificate Request Payload Format . . . . . . . . . . . . . . . . 28 12 Signature Payload Format . . . . . . . . . . . . . . . . . . . . . 29 13 Notification Payload Format . . . . . . . . . . . . . . . . . . . . 30 14 Notification Data - Acknowledge Message Type Format . . . . . . . . 32 15 Vendor ID Payload Format . . . . . . . . . . . . . . . . . . . . . 34 16 Key Creation Payload Format . . . . . . . . . . . . . . . . . . . . 34 17 Nonce Payload Format . . . . . . . . . . . . . . . . . . . . . . . 35 Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 4] INTERNET-DRAFT GSAKMP Light July 2002 List of Tables 1 Light Request to Join Message Definition . . . . . . . . . . . . . 13 2 Light Key Download Message Definition . . . . . . . . . . . . . . . 13 3 Light Acknowledgment Message Definition . . . . . . . . . . . . . . 14 4 Rekey Event Message Definition . . . . . . . . . . . . . . . . . . 15 5 Group Removal/Destruction Message Definition . . . . . . . . . . . 15 6 Group Identification Types . . . . . . . . . . . . . . . . . . . . 16 7 Payload Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8 Exchange Types . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9 Policy Token Types . . . . . . . . . . . . . . . . . . . . . . . . 20 10 Key Download Data Types . . . . . . . . . . . . . . . . . . . . . . 21 11 Rekey Event Types . . . . . . . . . . . . . . . . . . . . . . . . . 23 12 Identification Types . . . . . . . . . . . . . . . . . . . . . . . 25 13 Authorization Types . . . . . . . . . . . . . . . . . . . . . . . . 26 14 Certificate Payload Types . . . . . . . . . . . . . . . . . . . . . 27 15 Signature Types . . . . . . . . . . . . . . . . . . . . . . . . . . 29 16 Notify Messages Types . . . . . . . . . . . . . . . . . . . . . . . 31 17 Notify Messages -- Status Types . . . . . . . . . . . . . . . . . . 32 18 Acknowledgement Types . . . . . . . . . . . . . . . . . . . . . . . 33 19 Types Of Key Creation Information . . . . . . . . . . . . . . . . . 35 20 Nonce Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 5] INTERNET-DRAFT GSAKMP Light July 2002 1 Introduction The Group Secure Association Key Management Protocol (GSAKMP)[HCHMF01] is a general protocol for creating and managing cryptographic groups on a network. A cryptographic group is a logical association of users or hosts that support a common security policy using shared cryptographic keying material. The GSAKMP-Light (GL) profile of GSAKMP is a three message version of GSAKMP that does not require an underlying secure unicast security association. GL achieves this simplification by assuming that the group creation process includes the transmission to prospective members of an acceptable security suite for group establishment. While GSAKMP provides mechanisms for cryptographic group creation, other protocols may be used in conjunction with GSAKMP to allow various applications to create groups according to their application-specific requirements. For example, in a small-scale video conference the organizer might use a session invitation protocol like SIP [RFC2543] to transmit information about the time of the conference, the address of the session, and the formats to be used. For a large-scale video transmission, the organizer might use a multicast announcement protocol like SAP [RFC2974]. In both of these cases, non-sensitive information about the security mechanisms to be used in the cryptographic group establishment could easily be transmitted to the prospective group members. As we will show, including this information allows 2 messages to be removed from the group establishment portion of GSAKMP, producing the GSAKMP-Light (GL) profile. GSAKMP-Light provides a profile for the group establishment case where group members have been previously notified of a set of security mechanisms during the group announcement or invitation. The GSAKMP protocol includes mechanisms for group policy dissemination, group key dissemination, and group rekey operation. The GL profile shortens the policy and key dissemination steps, but does not limit or decrease the security of either of these operations. This profile of GSAKMP still contains the necessary mechanisms to facilitate policy enforcement and key management. Key management must be paired with policy enforcement to produce a viable secure association. As in GSAKMP, GL uses the policy definition stated in Internet Draft [HHMCD01] as the policy input to the enforcement process. While the GL profile does move some security profile information outside of the protocol, the entire policy token is still transmitted within the protocol. The transmission of a fully specified policy token to all joining group members is what allows GSAKMP to support distributed architectures and multiple data sources within a single cryptographic group. Distributed architectures are supported because the policy token allows rule-based allocation of Group Security Association actions to network resources. Multiple data sources are supported because the inclusion of a policy token and policy payloads allow group members to review the group access control and authorization parameters. This member review process gives each member and each potential source of data the ability to determine if the group Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 6] INTERNET-DRAFT GSAKMP Light July 2002 provides adequate protection for member data. The GL profile uses the same rekey operation as GSAKMP. This document repeats the specification for the rekey operation and GSAKMP payloads. This is to avoid having two draft documents getting out of synchronization. Like GSAKMP, the GL profile is provably secure, supports distributed architectures, allows multiple data sources within a single cryptographic group, and provides group management mechanisms. To facilitate the transmission of security mechanism settings during session invitation/announcement, this document also describes a useful default set of security algorithms and configurations, Security Suite 1. Full specification of this suite allows an entire set of algorithms and settings to be described to prospective group members in a concise manner. Future security suites can be defined as needed. 2 GSAKMP Light (GL) 2.1 Definitions Group Member: A group member (GM) is any entity with access to the group keys. Regardless of how a member becomes a part of the group or how the group is structured, GMs will perform the following actions: 1. Validate the authorizations for security relevant actions; 2. Accept group keys from the GC; 3. Request group keys from the GC; 4. Maintain local Certificate Revocation Lists (CRLs); 5. Enforce the cooperative group policies as stated in the group policy token; 6. Perform peer review of key management actions; and 7. Manage their local key. Group Secure Association (GSA): A cryptographic group is a logical association of users or hosts that share cryptographic key(s). This group may be established to support associations between applications or communication protocols. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 7] INTERNET-DRAFT GSAKMP Light July 2002 Group Policy: The group policy completely describes the protection mechanisms and security relevant behaviors of the group. This policy must be commonly understood and enforced by the group for coherent secure operations. Policy Token/Certificate: The policy token is a data structure used to disseminate group policy and the mechanisms to enforce it. The policy token is issued and signed by an authorized source. Each member of the group must verify the token, meet the group join policy, and enforce the policy of the group. The group policy data element will contain a variety of information including: 1. GSAKMP protocol format, 2. Key creation method, 3. Key dissemination policy, 4. Access control policy, 5. Group authorization policy, and 6. Compromise recovery policy. The policy token layout will be fully presented in the Group Policy Token Specification document. Group Controller: The Group Controller (GC) is a group member with authority to perform any critical protocol actions including: 1. Creating and distributing keys; 2. Maintain the Rekey infrastructure; and 3. Building and maintaining the Rekey arrays. As the group evolves, it may become desirable to have multiple controllers perform these functions (e.g., Rekey Controller and Group Key Controller). Subordinate Group Controller (SGC): Any group member, as defined in the group policy, and having the appropriate processing and trust characteristics, has the potential to act as a Subordinate Group Controller (SGC) thus allowing the group processing and communication requirements to be distributed equitably throughout the network. If the group is structured in such a way, the delegated group members would be identified via the policy token. The SGCs may perform actions delegated to them by the GC including: Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 8] INTERNET-DRAFT GSAKMP Light July 2002 1. Dissemination of the group key and 2. Management of the status of the local group. The ease of managing a very large group may also be improved by delegating the creation of subordinate LKH arrays Ref [WHA98] to the SGCs. The SGCs would have the authority and mechanisms necessary to create and disseminate the LKH arrays for the members under their control. A more detailed discussion of LKH arrays may be found in the Logical Key Hierarchy (LKH) Protocol document. Peer-to-Peer SA: Peer-to-Peer SA keys can be created by using any number of key generation protocols including the Internet Secure Association Key Management Protocol (ISAKMP)/IPSec [RFC 2401] and HS/SSL. These protocols rely on cooperative key generation algorithms and on peer review of permissions. Modern SA protocols are specifically developed to support this task. Once the peer-to-peer SA is established, the group protocol can use that SA mechanism for secure confidential peer communications throughout the life of the group. GSA Keys: GSA keys can be created using strong randomization key generation protocols. These protocols rely on a cooperatively conferred policy. Once the group keys are created and disseminated to the group members, the group protocol can use that SA mechanism for secure confidential group communications throughout the life of the group. Group Traffic Encryption Key (GTEK): The key or keys created for encrypting the group data. Logical Key Hierarchy (LKH) array: The group of keys created to facilitate the LKH compromise recovery methodology. Compromise Recovery: The act of recovering a secure operating state after detecting that a group member cannot be trusted. 3 Basis of security GSAKMP Light is based upon several existing protocols: ISAKMP [MSST98], GSAKMP, FIPS Pub 196 [FIPS 196], and Diffie-Hellman key exchange [DH77]. ISAKMP provided a flexible structure of chained payloads in support of authenticated key exchange and security association management for diverse pairwise communications. GSAKMP expanded upon these features to provide policy enforcement features in support of diverse group communications, and tunneling over existing security protocols. FIPS Pub 196 provides a mutual authentication protocol. Finally, Diffie-Hellman provides dynamic key exchange. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 9] INTERNET-DRAFT GSAKMP Light July 2002 Using the GSAKMP payloads, GSAKMP Light provides an authenticated security management protocol. Its message structure greatly parallels that of the FIPS Pub 196 mutual authentication exchange. Two points of departure: the first message of GSAKMP Light is signed and in the second and third messages, a nonce and combined nonce (hash of the two) is provided. The signature on the first message allows authenticated Diffie-Hellman, thereby preventing man-in-the-middle attacks. The digested combined nonce is a construct, which if a longer exchange were present would allow for only one value to be used after the third message. 4 Sequence of events The sequence of events for GL is straightforward. The sequence is: 1. Security suite definition is transmitted outside the protocol. 2. Light Request to Join (L-RTJ) 3. Light Key Download (L-KD) 4. Light Acknowledgement (L-ACK) 5. Group SA up and running 6. Group management The announcement will contain at a minimum the security suite for GL. Security Suite 1 is defined below. The member will initiate the following series of 3 messages for group establishment. - Light Request to Join initiates the GL group establishment portion of the protocol. L-RTJ contains a key creation field for use in group establishment. - Light Key Download contains a key creation field and encrypted Policy Token and Key Download payloads. - The Light Acknowledgement message completes the authentication of the GCKS for the member. Once a member has joined the group the GSA is considered up. Group management messages are multicast in nature and include rekey, policy changes, and group deletion. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 10] INTERNET-DRAFT GSAKMP Light July 2002 5 Security Policy GL recognizes that the distribution of a key is only relevant to the security of a system in so far as it represents a valid enforcement of security policy. 6 Security Suite 1 (SS1) GL is designed to support architectures with a capability to announce or otherwise prepublish the group establishment parameters. These group establishment parameters must contain enough information for a group member to configure GL. The SS1 defines the mandatory supported definition of Category one exchanges for GL. 6.1 Assumptions Assumption: There is a mechanism to either announce the Category 1 SA mechanisms to potential group members, post the Cat 1 policy, or inform group members of Cat 1 policy. In the case of an announced Category 1 policy it is desirable to have concise definitions of entire suites of algorithms and settings. To this end the authors define the GSAKMP Light Suite 1. 6.2 Definition Suite 1 GSAKMP Light implementations must support the following suite of algorithms and configurations. The following definition of Suite 1 borrows heavily from IKE's Oakley group 2 definition and Oakley itself. The GSAKMP Light suite 1 definition defines all the algorithm and cryptographic definitions required to process the default mode of GSAKMP Light. It is important to note that GSAKMP Light does not negotiate these cryptographic modes. This definition is set by the Group Owner via the Policy Token (passed during the GSAKMP Light exchange for member verification purposes). The GSAKMP Light Suite definition is: Key download encryption algorithm definition: Algorithm: 3DES Mode: CBC64 Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 11] INTERNET-DRAFT GSAKMP Light July 2002 Key Length: 192 bits Policy Token encryption algorithm definition: Algorithm: 3DES Mode: CBC64 Key Length: 192 bits The Key Creation definition is: Algorithm type is Diffie Hellman MODP group definition g: 2 p: "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381" "FFFFFFFF FFFFFFFF" NOTE: The p {\&} g values comes from rfc 2409, IKE, section 6.2 Second Oakley Group, and p is 1024 bits long. The digital signature algorithm is: DSS-ASN1-DER Hash algorithm is: SHA-1 7 Message Structure 7.1 Flow Diagram The Light Group Establishment Flow Diagram is shown in Figure 1: CONTROLLER MESSAGE MEMBER !<------------Request to Join-------------! ! ! !-------------Key Download--------------->! ! ! !<------------Acknowledgment--------------! Figure 1: GSAKMP Light Ladder Diagram Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 12] INTERNET-DRAFT GSAKMP Light July 2002 7.2 Light Request to Join The components of a Light Request to Join Message are shown in Table 1: Table 1: Light Request to Join Message Definition Message Name : L-RTJ Dissection : {HDR, GrpID, Key Creation, Nonce_I} SigM, [CertM] Payload Types : GSAKMP Header, Key Creation, Nonce, Signature, [Certificate] SigM : Signature of Group Member CertM : Certificate of Group Member {}SigX :Indicates minimum fields used in Signature [] : Indicate an optional data item 7.3 Light Key Download The components of a Light Key Download Message are shown in Table 2: Table 2: Light Key Download Message Definition Message Name : L-KD Dissection : {HDR, GrpID, Member ID, Nonce_R, Nonce_C, Key Creation, (Policy Token)*, (Key Download)*} SigC, [CertC] Payload Types : GSAKMP Header, Identification, Nonce, Key Creation, Policy Token, Key Download, Signature, [Certificate] SigC : Signature of Group Controller CertC : Certificate of Group Controller {}SigX :Indicates minimum fields used in Signature [] : Indicate an optional data item (data)* : Indicates encrypted information 7.4 Light Acknowledgement The components of a Light Acknowledgement Message are shown in Table 3: 7.5 Group Maintenance The Group Maintenance phase includes member joins and leaves, group rekey activities, and the management of Rekey events. These activities are Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 13] INTERNET-DRAFT GSAKMP Light July 2002 Table 3: Light Acknowledgment Message Definition Message Name : Acknowledgment Dissection : {HDR, GrpID, Nonce_C, ACK}SigM Payload Types : GSAKMP Header, Nonce, Notification, Signature SigM : Signature of Group Member CertM : Certificate of Group Member {}SigX :Indicates minimum fields used in Signature presented in the following sections. 7.5.1 Member Joins/Leaves The addition of group members to a previously established group will closely follow the processing presented in Sections 7.1 through 7.4. With the exception of the pure group establishment tasks (e.g., creation of policy token, GTEK, and Rekey array), an entity becomes a GM using the same message exchanges described in Sections 7.1 through 7.4. A member who elects to voluntarily leave the group will be responsible for destroying his key. Any further action for a voluntary leave should be specifically addressed in the group's security policy. 7.5.2 Rekey Events A Rekey event is any action, including compromises, that involves the creation and dissemination of a new group key and/or Rekey information. Once it has been identified, using the group's security policy, that a Rekey event has occurred, the GC must create and send a signed message containing the GTEK and Rekey array to the group. Each GM who receives this message must verify the signature on the message to ensure its authenticity. If the message signature does not verify, the processing is terminated. GSAKMP sends a properly authenticated message with a Notification Payload of type NACK to indicate termination. Upon verification the GM will find the appropriate Rekey download packet and decrypt the information with a stored Rekey key. The components of a Rekey Event message are shown in Table 4: Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 14] INTERNET-DRAFT GSAKMP Light July 2002 Table 4: Rekey Event Message Definition Message Name : Rekey Event Dissection : {HDR, GrpID, [Policy Token], Rekey Array}SigC, [CertC] Payload Types : GSAKMP Header, [Policy Token], Rekey Event, Signature, [Certificate], [Vendor ID] SigC : Signature of Group Controller CertC : Certificate of Group Controller {}SigX :Indicates minimum fields used in Signature [] : Indicate an optional data item 7.5.3 Group Removal/Destruction At this point in the group's life-cycle, there has been a decision to destroy the group and the notification is broadcast on a key management channel or through a directory service. The components of a Group Removal/Destruction message are shown in 5: Table 5: Group Removal/Destruction Message Definition Message Name : Group Removal/Destruction Dissection : {HDR, GrpID, [Policy Token], Destruct}SigC, [CertC] Payload Types : GSAKMP Header, [Policy Token], Notification, Signature, [Certificate], [Vendor ID] SigC : Signature of Group Controller CertC : Certificate of Group Controller {}SigX :Indicates minimum fields used in Signature [] : Indicate an optional data item 8 GSAKMP Payload Structure 8.1 GSAKMP Header The GSAKMP Header fields are defined in Figure 2: Group Identification Type (1 octet) - Table 6 presents the group identification types. Group Identification Value (8 octets) - Indicates the name/title of the Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 15] INTERNET-DRAFT GSAKMP Light July 2002 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! !Group ID Type ! Group ID Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ ! Next Payload ! Version ! Exchange Type ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Sequence ID ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 2: GSAKMP Header Format Table 6: Group Identification Types Grp ID Type Value _____________________ IPSec IPv4 0 IPSec IPv6 1 TLS 2 SMIME 3 Other 4-255 group. Next Payload (1 octet) - Indicates the type of the first payload in the message. The format for each payload is defined in the following sections. Table 7 presents the payload types. Version (1 octet) - Indicates the version of the GSAKMP protocol in use. Exchange Type (1 octet) - Indicates the type of exchange (also known as the message type). Table 8 presents the exchange type values. Sequence ID (4 octets) - Group Management replay protection field. Sequence ID for group management messages. If not a group management message, this value is set to zero (0). Length (4 octets) - Length of total message (header + payloads) in octets. Encryption can expand the size of a GSAKMP message. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 16] INTERNET-DRAFT GSAKMP Light July 2002 Table 7: Payload Types Next_Payload_Type Value ___________________________________ None 0 Policy Token 1 Key Download Packet 2 Rekey event 3 Identification 4 Authorization 5 Certificate 6 Certificate Request 7 Signature 9 Notification 10 Vendor ID 11 Key Creation 12 Nonce 13 Reserved 14 - 127 Private Use 128 -- 255 Table 8: Exchange Types Exchange_Type Value ____________________________________ Request to Join 0 Invitation 1 Invitation Response 2 Key Download 3 Acknowledgement 4 Rekey Event 5 Group Removal/Destruction 6 No Message 7 Light Request to Join 8 Light Key Download 9 Other 10-255 Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 17] INTERNET-DRAFT GSAKMP Light July 2002 8.2 Generic Payload Header Each GSAKMP payload defined in the following sections begins with a generic header, shown in Figure 3, which provides a payload ``chaining`` capability and clearly defines the boundaries of a payload. The Generic Payload Header fields are defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 3: Generic Payload Header Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. 8.3 Data Attributes Payload There are instances within GSAKMP where it is necessary to represent Data Attributes. These Data Attributes are not a GSAKMP payload, but are contained within GSAKMP payloads. The format of the Data Attributes provides the flexibility for representation of many different types of information. There can be multiple Data Attributes within a payload. The length of the Data Attributes will either be 4 octets or defined by the Attribute Length field. This is done using the Attribute Format bit described in Figure 4. The Data Attributes fields are defined as follows: Attribute Type (2 octets) - Unique identifier for each type of attribute. The most significant bit, or Attribute Format (AF), indicates whether the data attributes follow the Type/Length/Value (TLV) format or a shortened Type/Value (TV) format. If the AF bit is a zero (0), then the Data Attributes are of the Type/Length/Value (TLV) form. If the AF bit is a one (1), then the Data Attributes are of the Type/Value form. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 18] INTERNET-DRAFT GSAKMP Light July 2002 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Attribute Type ! AF=0 Attribute Length ! ! ! AF=1 Attribute Value ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! AF=0 Attribute Value ~ ! AF=1 Not Transmitted ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 4: Data Attributes Payload Attribute Length (2 octets) - Length in octets of the Attribute Value. When the AF bit is a one (1), the Attribute Value is only 2 octets and the Attribute Length field is not present. Attribute Value (variable length) - Value of the attribute associated with the GSAKMP-specific Attribute Type. If the AF bit is a zero (0), this field has a variable length defined by the Attribute Length field. If the AF bit is a one (1), the Attribute Value has a length of 2 octets. 8.4 Policy Token Payload The Policy Token Payload contains group specific information that describes the group security relevant behaviors, access control parameters, and security mechanisms. This information may contain a digital signature(s) to prove authority and integrity of the information. Figure 5 shows the format of the payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! ID Type ! Policy Token Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 5: Policy Token Payload Format The Policy Token Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 19] INTERNET-DRAFT GSAKMP Light July 2002 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Key Download Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 6: Key Download Payload Format RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. ID Type (1 octet) - Specifies the type of Policy Token being used. Table 9 identifies the types of policy tokens. Table 9: Policy Token Types ID_Type Value ______________________ Group 0 Auxiliary 1 Reserved 2-63 Unassigned 64-255 Policy Token Data (variable length) - Contains Policy Token information. The values for this field are group specific and the format is specified by the ID Type field. The payload type for the Policy Token Payload is one (1). 8.5 Key Download Payload The Key Download Payload contains group keys. These key download payloads can have several security attributes applied to them based upon the security policy of the group. Figure 6 shows the format of the payload. If the security policy of the group dictates, the key download payload may be encrypted with a key exchange key (KEK). The type of encryption used is specified in the Policy Token. The group members may create the KEK using the key creation method identified in the Key Creation Payload. The Key Download Payload fields are defined as follows: Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 20] INTERNET-DRAFT GSAKMP Light July 2002 Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Key Download Data (variable length) - Contains Key Download information. Number of Key Packets (2 octets) -- Contains the total number of both GTEK and Rekey arrays being passed in this data block. For each Key Packet, the data format is as follows: Key Download Data (KDD) Type (1 octet) -- Identifier for the Key Data field of this Key Packet. See Table 10 for the possible values of this field. Table 10: Key Download Data Types Key Download Data Type Value ________________________________ GTEK 0 Rekey 1 Unassigned 2-255 Key Download Length (2 octets) -- Length in octets of the Key Packet data following this field. Key Packet Data (variable length) -- Contains Key information. The format of this field is specific depending on the value of the Key Download Data field. 8.5.1 GTEK Key Packet For a Key Download Data value of GTEK, the Key Packet Data field is formatted as follows: Key Type (1 octet) -- This is the encryption algorithm for which this key data is to be used. This value is specified in the Policy Token. Key Creation Date (4 octets) -- This is the time value of when this key Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 21] INTERNET-DRAFT GSAKMP Light July 2002 data was originally generated. Key Expiration Date (4 octets) -- This is the time value of when this key is no longer valid for use. Key Handle (4 octets) -- This is the randomly generated value to uniquely identify a key. Key Data (variable length) -- This is the actual encryption key data, which is dependent on the Key Type algorithm for its format. 8.5.2 Rekey Key Packet GSAKMP currently uses the Logical Key Hierarchy (LKH) protocol for Rekey operations. This Key Packet Data is assumed to contain LKH Array data of the following format: LKH Version (1 octet) -- Contains the version of the LKH protocol which the data is formatted in. Leaf ID (2 octets) -- This is the Leaf Node ID of the LKH sequence contained in this Key Packet Data block. Number of LKH Keys (2 octets) -- This value is the number of distinct LKH keys in this sequence. For each LKH key in the sequence, the data format is as follows: LKH ID (2 octets) -- This is the position of this key in the binary tree structure used by LKH. Key Type (1 octet) -- This is the encryption algorithm for which this key data is to be used. This value is specified in the Policy Token. Key Creation Date (4 octets) -- This is the time value of when this key data was originally generated. Key Expiration Date (4 octets) -- This is the time value of when this key is no longer valid for use. Key Handle (4 octets) -- This is the randomly generated value to uniquely identify a key. Key Data (variable length) -- This is the actual encryption key data, which is dependent on the Key Type algorithm for its format. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 22] INTERNET-DRAFT GSAKMP Light July 2002 The payload type for the Key Download Packet is two (2). 8.6 Rekey Event Payload The Rekey Event Payload contains multiple keys encrypted in Rekey keys. These Rekey Event payloads can have several security attributes applied to them based upon the security policy of the group. Figure 7 shows the format of the payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! ID Type ! Rekey Event Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 7: Rekey Event Payload Format The Rekey Event Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. ID Type (1 octet) - Specifies the type of Rekey Event being used. Table 11 presents the types of Rekey events. Table 11: Rekey Event Types ID_Type Value ______________________________ None 0 Group Recovery 1 Individual Recovery 2 Maintenance 3 Delete Group Key 4 Unassigned 5-255 Rekey Event Data (variable length) - Contains Rekey Event information. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 23] INTERNET-DRAFT GSAKMP Light July 2002 The values for this field are group specific and the format is specified by the ID Type field. The format for the LKH type of Rekey Event Data is located in the appendix section. The Rekey Event payload type is three (3). 8.7 Identification Payload The Identification Payload contains entity-specific data used to exchange identification information. This information is used for determining the identities of negotiating members and may be used for determining authenticity of information. Figure 8 shows the format of the Identification Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! ID Type ! Identification Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 8: Identification Payload Format The Identification Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. ID Type (1 octet) - Specifies the type of Identification being used. Table 12 identifies the types of identities. Identification Data (variable length) - Contains identity information. The values for this field are group-specific and the format is specified by the ID Type field. The payload type for the Identification Payload is four (4). Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 24] INTERNET-DRAFT GSAKMP Light July 2002 Table 12: Identification Types ID_Type Value _____________________________________________ Sender Distinguished Name 0 Receiver Distinguished Name 1 Hash of Sender Distinguished Name 2 Hash of Receiver Distinguished Name 3 Unassigned 4-255 8.8 Authorization Payload The Authorization Payload contains group-specific data used to exchange role authorization information. This information is used for determining the authorization of entities within a group. Figure 9 shows the format of the Authorization Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Auth Type ! Authorization Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 9: Authorization Payload Format The Authorization Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Authorization Type (1 octet) - Specifies the type of role authorization being used. Table 13 identifies the types of roles. Authorization Data (variable length) - Contains authorization information. The values for this field are group-specific and the format is specified by the Authorization Type field. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 25] INTERNET-DRAFT GSAKMP Light July 2002 Table 13: Authorization Types Auth_Type Value ________________________________________________ Group Controller 0 Group and Rekey Controller 1 Rekey Controller 2 Subordinate Group Controller 3 Subordinate Group and Rekey Controller 4 Subordinate Rekey Controller 5 Member ID 6 Unassigned 7-255 The payload type for the Authorization Payload is five (5). 8.9 Certificate Payload The Certificate Payload provides a means to transport certificates or other certificate-related information via GSAKMP and can appear in any GSAKMP message. Certificate payloads SHOULD be included in an exchange whenever an appropriate directory service (e.g. Secure DNS [DNSSEC]) is not available to distribute certificates. The Certificate payload MUST be accepted at any point during an exchange. Figure 10 shows the format of the Certificate Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Cert Encoding ! Certificate Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 10: Certificate Payload Format The Certificate Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 26] INTERNET-DRAFT GSAKMP Light July 2002 including the generic payload header. Certificate Encoding (1 octet) - This field indicates the type of certificate or certificate-related information contained in the Certificate Data field. Table 14 presents the types of certificate payloads. Table 14: Certificate Payload Types Certificate_Type Value _______________________________________________ None 0 PKCS #7 wrapped X.509 certificate 1 PGP Certificate 2 DNS Signed Key 3 X.509 Certificate -- Signature 4 X.509 Certificate - Key Exchange 5 Kerberos Tokens 6 Certificate Revocation List (CRL) 7 Authority Revocation List (ARL) 8 SPKI Certificate 9 X.509 Certificate -- Attribute 10 Reserved 11 -- 255 Certificate Data (variable length) - Actual encoding of certificate data. The type of certificate is indicated by the Certificate Encoding field. The payload type for the Certificate Payload is six (6). 8.10 Certificate Request Payload The Certificate Request Payload provides a means to request certificates via GSAKMP and can appear in any message. Certificate Request payloads SHOULD be included in an exchange whenever an appropriate directory service (e.g., Secure DNS [DNSSEC]) is not available to distribute certificates. The Certificate Request payload MUST be accepted at any point during the exchange. The responder to the Certificate Request payload MUST send its certificate, if certificates are supported, based on the values contained in the payload. If multiple certificates are required, then multiple Certificate Request payloads SHOULD be transmitted. Figure 11 shows the format of the Certificate Request Payload. The Certificate Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 27] INTERNET-DRAFT GSAKMP Light July 2002 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Cert Type ! Certificate Authority ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 11: Certificate Request Payload Format payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Certificate Type (1 octet) - Contains an encoding of the type of certificate requested. Certificate Authority (variable length) - Contains an encoding of an acceptable certificate authority for the type of certificate requested. As an example, for an X.509 certificate this field would contain the Distinguished Name encoding of the Issuer Name of an X.509 certificate authority acceptable to the sender of this payload. This would be included to assist the responder in determining how much of the certificate chain would need to be sent in response to this request. If there is no specific certificate authority requested, this field SHOULD NOT be included. The payload type for the Certificate Request Payload is seven (7). 8.11 Signature Payload The Signature Payload contains data generated by the digital signature function. The digital signature covers the Signature Payload Span and the Signature Payload up to the Signature Data. The exception to this is if the signature algorithm used is DSS with ASN.1/DER encoding. Due to the variable length of a DER encoding, the signature span across the signature payload itself only extends up to the signature data length field, not the signature data. Figure 12 shows the format of the Signature Payload. The Signature Payload fields are defined as follows: Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 28] INTERNET-DRAFT GSAKMP Light July 2002 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Sig Type ! Signature Payload Span ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ ! Sig ID Role ! Signature Timestamp ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ ! Signer ID Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ Signer ID Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Signature Length ! Signature Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 12: Signature Payload Format Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Signature Type (1 octet) -- Indicates the type of signature. Table 15 presents the Signature Types. Table 15: Signature Types Signature Type Value _____________________________________ DSS with ASN.1/DER encoding 0 DSS without encoding 1 Other 2-255 Signature Payload Span (4 octets) - Identifies the information included in the signature. The first two octets define the first signature payload. The third and fourth octet define the last payload. The payloads in the message are an ordered sequence beginning at the header, with a value of 0. If the signature payload itself is not in the signature span, you must still sign over the signature payload up to the signature data. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 29] INTERNET-DRAFT GSAKMP Light July 2002 Signature ID Role (1 octet) -- Specifies the type of Authorization (Role) being used. Refer to Table 13 for the types of authorization (role). Signature Timestamp (4 octets) -- Date and time that the digital signature was applied. Signer ID Length (2 octets) - Length in octets of the Signer' ID. Signer ID (variable length) -- Data identifying the Signer's ID (e.g., DN). Signature Length (2 octets) -- Length in octets of the Signature Data. Signature Data (variable length) - Data that results from applying the digital signature function to the GSAKMP message and/or payload. The payload type for the Signature Payload is nine (9). 8.12 Notification Payload The Notification Payload can contain both GSAKMP and group specific data and is used to transmit informational data, such as error conditions, to a GSAKMP peer. It is possible to send multiple Notification payloads in a single GSAKMP message. Figure 13 shows the format of the Notification Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Notify Message Type ! STATUS TYPE ! ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ~ Notification Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 13: Notification Payload Format The Notification Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 30] INTERNET-DRAFT GSAKMP Light July 2002 Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Notify Message Type (2 octets) - Specifies the type of notification message. Table 16 presents the Notify Message Types. Table 16: Notify Messages Types Information Value _______________________________________________ None 0 Invalid-Payload-Type 1 Situation-Not-Supported 2 Invalid-Major-Version 3 Invalid-Version 4 Invalid-Group-ID 5 Invalid-Message-ID 6 Payload-Malformed 7 Invalid-Key-Information 8 Invalid-ID-Information 9 Invalid-Cert-Encoding 10 Invalid-Certificate 11 Cert-Type-Unsupported 12 Invalid-Cert-Authority 13 Authentication-Failed 14 Invalid-Signature 15 Notify-GSA-Lifetime 16 Certificate-Unavailable 17 Unequal-Payload-Lengths 18 Unauthorized Request 19 Unable To Take Requested Role 20 Group Deleted 21 Request To Join 22 Acknowledgement 23 Invitation 24 Invitation-Response 25 Nack 26 Reserved (future use) 27 - 8191 Private Use 8192 -- 16383 Status Type (1 octet) - Specifies the status of group with respect to originator of notification. Notification information specifies status data and can be used by a process managing a SA database to communicate with a peer process. For example, a secure front end or security gateway may use the Notify message to synchronize SA communication. Table 17 presents the Notification Message Status Types. Notification Data (variable length) - Informational or error data transmitted in addition to the Notify Message Type. Values for this Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 31] INTERNET-DRAFT GSAKMP Light July 2002 Table 17: Notify Messages -- Status Types Status Value ____________________________________ Not connected 0 Establishing group 1 Connected to group 2 Previously member of group 3 Reserved (future use) 4-255 field are Domain of Interpretation (DOI)-specific. The payload type for the Notification Payload is ten (10). 8.12.1 Notification Data - Acknowledgement (ACK) Message Type The data portion of the ACK payload serves either for confirmation of correct receipt of the Key Download message, or, when needed, can provide non-repudiation of receipt when included in a signed message. Figure 14 shows the format of the Notification Data - Acknowledge Message Type. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Ack Type ! Acknowledgement Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 14: Notification Data - Acknowledge Message Type Format The Notification Data - Acknowledgement Message Type data fields are defined as follows: Ack Type (1 octet) - Specifies the type of acknowledgement message. Table 18 presents the Notify Acknowledgement Message Types. Simple - Data portion null. MD5 MAC - Data portion contains output of MD5 HMAC function [RFC 2104]. Input to HMAC function is the Nonce_C value appended to the decrypted portion, sans encryption padding, of the Key Download payload of the received Key Download Packet. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 32] INTERNET-DRAFT GSAKMP Light July 2002 Table 18: Acknowledgement Types ACK_Type Value ____________________ Simple 0 MD5 MAC 1 SHA-1 HMAC 2 Unassigned 3-255 SHA-1 HMAC - Data portion contains output of SHA-1 HMAC function [RFC 2104]. Input to HMAC function is the Nonce_C value appended to the decrypted portion, sans encryption padding, of the Key Download payload of the received Key Download Packet. 8.13 Vendor ID Payload The Vendor ID Payload contains a vendor defined constant. The constant is used by vendors to identify and recognize remote instances of their implementations. This mechanism allows a vendor to experiment with new features while maintaining backwards compatibility. This is not a general extension facility of GSAKMP. Figure 15 shows the format of the Vendor ID Payload. The Vendor ID payload is not an announcement from the sender that it will send private payload types. A vendor sending the Vendor ID MUST NOT make any assumptions about private payloads that it may send unless a Vendor ID is received as well. Multiple Vendor ID payloads MAY be sent. An implementation is NOT REQUIRED to understand any Vendor ID payloads. An implementation is NOT REQUIRED to send any Vendor ID payload at all. If a private payload was sent without prior agreement to send it, a compliant implementation may reject a proposal with a notify message of type INVALID-PAYLOAD-TYPE. The vendor defined constant MUST be unique. The choice of hash and text to hash is left to the vendor to decide. As an example, vendors could generate their vendor id by taking a plain (non-keyed) hash of a string containing the product name, and the version of the product. The Vendor ID Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 33] INTERNET-DRAFT GSAKMP Light July 2002 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Vendor ID (VID) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 15: Vendor ID Payload Format Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Vendor ID (variable length) - Hash of the vendor string plus version (as described above). The payload type for the Vendor ID Payload is eleven (11). 8.14 Key Creation Payload The Key Creation Payload contains information used to create key encryption keys. These key creation payloads can have security attributes applied to them based upon the security policy of the group. Figure 16 shows the format of the payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! ID Type ! Key Creation Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 16: Key Creation Payload Format The Key Creation Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 34] INTERNET-DRAFT GSAKMP Light July 2002 Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. ID Type (1 octet) - Specifies the type of Key Creation being used. Table 19 identifies the types of key download information. Table 19: Types Of Key Creation Information ID_Type Value ________________________ Reserved 0 Diffie-Hellman 1 other 2-255 Key Creation Data (variable length) - Contains Key Creation information. The values for this field are group specific and the format is specified by the ID Type field. The payload type for the Key Creation Packet is twelve (12). 8.15 Nonce Payload The Nonce Payload contains random data used to guarantee freshness during an exchange and protect against replay attacks. Figure 17 shows the format of the Nonce Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ! Nonce Type ! Nonce Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! Figure 17: Nonce Payload Format The Nonce Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. RESERVED (1 octet) - Unused, set to 0. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 35] INTERNET-DRAFT GSAKMP Light July 2002 Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. Nonce Type (1 octet) - Specifies the type of Nonce being used. Table 20 identifies the types of nonces. Table 20: Nonce Types Nonce_Type Value Definition __________________________________________________________________________ None 0 Initiator 1 Responder 2 Combined 3 Hash ( Append (Initiator_Value, Responder_Value) ) Unassigned 4-255 Nonce Data (variable length) - Contains the nonce information. The values for this field are group-specific and the format is specified by the Nonce Type field. If no group-specific information is provided, the minimum length for this field is 4 bytes. The payload type for the Nonce Payload is thirteen (13). 9 References and authors addesses The following references were used in the preparation of this document. 9.1 References [HCHMF01] H. Harney, A. Colegrove, E. Harder, U. Meth, R. Fleischer, Group Secure Association Key Management Protocol, draft-ietf-msec-gsakmp-sec-00, March 2001 [HHMCD01] , Thomas Hardjono, Hugh Harney, Pat McDaniel, Andrea Colgrove, Pete Dinsmore, Group Security Policy Token: Definition and Payloads', draft-ietf-msec-gspt-00.txt, Work in progress. [MSST98] Maughan, D., Schertler, M., Schneider, M., and J. Turner, ``Internet Security Association and Key Management Protocol (ISAKMP)'', RFC 2408, November 1998. [FIPS 196], ``Entity Authentication Using Public Key Cryptography,'' Federal Information Processing Standards Publication 196, NIST, February 1997. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 36] INTERNET-DRAFT GSAKMP Light July 2002 [DH77], Diffie, W., and M. Hellman, ``New Directions in Cryptography'', IEEE Transactions on Information Theory, June 1977. [WHA98], Wallner, D., Harder E., and Agee R., ``Key Management for Multicast: Issues and Architectures'', Internet Draft, Informational, September 1998. [BMS], Balenson D., McGrew D., Sherman A., ``Key Management for Large Dynamic Groups: One-Way Function Trees and Amortized Initialization'', Internet Draft, February 1999. [RFC 2093] Harney H., Muckenhirn C., and Rivers T., ``Group Key, Management Protocol Specification'', RFC 2093, Experimental, July 1997. [RFC 2094] Harney H., Muckenhirn C., and Rivers T., ``Group Key Management Protocol Architecture'', RFC 2094, Experimental, July 1997. [RFC 2104] Krawczyk H., Bellare M., and Canetti R., ``HMAC: Keyed-Hashing for Message Authentication'', RFC 2104, Informational, February [RFC 2401] Kent S. and Atkinson, R., ``Security Architecture for the Internet Protocol'', RFC 2401, November 1998, Proposed Standard. [RFC 2402] Kent S. and Atkinson, R., ``IP Authentication Header'', RFC 2402, November 1998, Proposed Standard.1997. [RFC 2406] Kent S. and Atkinson, R., ``IP Encapsulating Security Payload (ESP)'', RFC 2406, November 1998, Proposed Standard. [RFC 2408] Maughan D., Schertler M., Schneider M., and Turner J., ``Internet Security Association and Key Management Protocol (ISAKMP)'', RFC 2408, Proposed Standard, November 1998. [RFC 2409] Harkins D. and Carrel D., ``The Internet Key Exchange (IKE)'', RFC 2409, Proposed Standard, November 1998. [RFC 2412] Orman H. K., ``The OAKLEY Key Determination Protocol'', RFC 2412, Informational, November 1998. [RFC2543], M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg, SIP: Session Initiation Protocol, March 99 [RFC2974], M. Handley, C. Perkins, E. Whelan, Session Announcement Protocol, Oct 2000. Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 37] INTERNET-DRAFT GSAKMP Light July 2002 9.2 Authors Addresses Hugh Harney (point-of-contact) 9861 Broken Land Parkway Suite 300 Columbia, MD 21046 (410) 381-9400 ext 203 FAX (410) 381-5559 hh@columbia.sparta.com Angela Schuett R231 NSA 9800 Savage Rd Suite 6534 Fort Meade, MD 20755 (301) 688-0850 FAX (301) 688-0255 amschue@tycho.ncsc.mil Andrea Colegrove 9861 Broken Land Parkway Suite 300 Columbia, MD 21046 (410) 381-9400 ext 232 FAX (410) 381-5559 acc@columbia.sparta.com Document expiration: December 31, 2002 Harney/Schuett/Colegrove draft-ietf-msec-gsakmp-light-sec-01.txt [Page 38]